1. Field of the Invention
This invention relates to an electronic circuit and a method of producing an integrated electronic circuit comprising at least one electronic component, in particular a power electronic component, in a substrate plate.
In the sense of this invention, by electronic component, one understands both an individual component such as a diode, or a transistor and an operational assembly of components such as an amplification stage or a logic switching unit.
In addition, by component, one understands by power component, a component through which large currents are able to pass or a component capable of receiving at its terminals, high voltages. Such components are, for example, diodes, transistors, and thyristors capable of operating at voltages which, depending on the application, can reach several thousands of volts and/or through which currents of several tens of amps can pass.
The invention finds application in the manufacture of electric motor control circuits, protection circuits, such as circuit breaker circuits, power limiters or regulators, or in circuits that combine logic switching stages and power switching stages.
2. Description of the Prior Art
The integrated circuits for controlling motors or power regulation circuits generally comprise one or more power components that can occupy a large area on an integration substrate of up to several mm2 per component. It also comprises electronic command components connected to the power components, the command components operating at low voltage and with a low current.
The imperatives of manufacturing cost and the space occupied lead one to bring together the power components and the other components of the circuit into a single monolithic unit capable of being manufactured in accordance with collective process techniques.
The manufacture of monolithic units that integrate all the components of a circuit, generally comprises the integration of the power components and the other components into one and the same substrate plate.
This integration then poses problems of electrical insulation which require either modification of the components themselves, favoring manufacturing techniques for the components at the surface, to the detriment of manufacturing within the thickness of the substrate plate, or demands complicated preparation of the substrates before the production of the components.
This preparation work for electrical insulation may comprise the diffusion of doping impurities, at high temperature, into the substrate plate so as to form junction barriers. According to other techniques, the insulation can be provided by creating dielectric walls (enclosures) within the substrate before integrating the components into it.
Modification of the components themselves or preparation of the substrate involve complex and expensive operations which are generally not very compatible with the demands of high manufacturing output performance and of high density integration of components.
The aim of this invention is to provide a method of manufacturing an integrated electronic circuit that can comprise both power electronic components and other electronic components and does not have the difficulties mentioned above.
A particular aim is to provide such a method which does not impose any restriction whatsoever on the manufacture or the modification of the components themselves in order to achieve their mutual electrical installation.
Another aim is to provide a method that enables the integration of all the components into one and the same substrate without any particular preparation of the substrate.
A further aim is to provide a method that makes possible more effective insulation of components operating at high voltage and components operating at low voltage.
Another aim is to provide a method that permits the production of monolithic units comprising all the components of an electronic circuit, the external faces of which are substantially free of connection terminals. The absence of connection terminals on the external faces offers the possibility of fitting radiator units for heat dissipation.
Yet another aim of the invention is to provide such a method that allows collective and simultaneous manufacture of a large number of identical electronic circuits.
In order to achieve these aims, the invention provides a method of producing an integrated circuit comprising a plurality of electrical components, one or more of which are, for example power components. The method comprises the following successive steps:
a) forming a plurality of components in a substrate plate, and forming connection points for said components, on a first face of the substrate plate,
b) forming on a connection support conducting tracks according to a pattern that corresponds with connection points distribution on the substrate plate,
c) transferring the substrate plate onto the connection support, electrically connecting the connection points with the corresponding conducting tracks,
d) forming at least one separation trench in the substrate plate, surrounding at least one portion of substrate that includes at least one electronic component, in a way that separates it from other electronic components in the substrate plate, the separation trench passing right through the substrate plate without reaching the connections support, and
e) filling the trenches with a dielectric material.
The formation of separation trenches combined with their filling with a dielectric material allows one effectively to insulate the various portions of substrate that each include one or more electronic components. In particular it is possible to mutually insulate portions of substrate that include power components, in particular high voltage power components, and portions of substrate that include components operating at low voltage.
This particular feature of the invention allows one initially to produce all the components in one and the same substrate plate without worrying about their electrical insulation. Hence, the methods of manufacturing the components can be chosen freely and in relation to imperatives other than the electrical insulation, and the substrate plate does not require any special preparation.
Furthermore, as the formation of the trenches is subsequent to transfer of the substrate plate onto the connection support, the connection of all the components can take place in a collective and simultaneous fashion.
This particular feature is advantageous notably within the context of industrial manufacture of integrated circuits.
According to one particular embodiment of the method, before step c), flaring grooves can be made in the substrate plate for the trenches in places where it is intended to form trenches in step d).
Flaring the ends of the trenches enables one to prevent the edges of the portions of substrate plate on each side of the trenches forming sharp edges and concentrating an electric field that exists between the portions of the substrate plate. Hence the behavior at voltage between the different portions can be improved.
The flaring grooves can be made with chamfered edges, using a saw blade with an oblique edge. They may also be made by etching, giving the edges a rounded shape.
During step c) of the method, the contact points and the conducting tracks can be connected by a connection method chosen, for example, from connection through bosses of fusible material, connection through a conductive adhesive, or connection through eutectic soldering.
Connection through bosses and particularly through beads of fusible material is preferred particularly when the number of connection points for the components is high. Furthermore, the technique of connection through beads of fusible material, also known under the name of xe2x80x9cFlip chipxe2x80x9d, permits transfer of the substrate plate onto the connection support with greater alignment tolerances. In effect, precise mutual positioning between the substrate plate and the support is automatically provided through the effect of surface tension forces which are exerted within the bead material, when it is molten.
When the connection is made through beads of fusible material, it is possible, during step e) of the method, for the dielectric material introduced through the trenches, to penetrate between the substrate plate and the connection support, so as to envelope said beads.
Putting dielectric material into all the free space between the substrate plate and the connection support allows one to control precisely the electrical insulation between the components and also between the beads of fusible material used as an electrical connection.
After the dielectric material has been put into place, the procedure can be completed by the formation of contact points and interconnection tracks on a second free face of the substrate plate, opposite said first face.
Such interconnection of components through the xe2x80x9cback facexe2x80x9d is particularly suggested for the power components.
Preferably, in order to make the connections on the second face of the substrate plate, it is desirable that this face has a flat surface. Also, putting the dielectric material into the trenches is done in such a way that the material is exactly flush with the surface of the second plate.
According to another advantageous aspect of the invention, the method can comprise, in addition, the laying bare of a part of the connection support, into which at least one conducting track connected to at least one of the components extends.
This characteristic permits access to conducting tracks for the purpose of making connections to the outside, and therefore of limiting or doing away with connection sockets on the free external faces of the substrate plate or the support.
These faces can then be brought into contact with radiators for the dissipation of the heat produced by the power components.
The invention also relates to an integrated circuit comprising a plurality of components, formed in portions of a substrate separated by trenches, a support plate for the portions of substrate, fitted with conducting tracks connected to the components, and a dielectric material extending within said trenches and, at least in part, between portions of the substrate and the support plate. Such a circuit can be obtained by the method described above.
It may comprise power components and logic switching components formed in different portions of the substrate.
Other characteristics and advantages of this invention will better emerge from the description which follows, and which refers to the figures of the appended drawings. This description is given purely for illustrative purposes only and is non-limitative.